- General pathology
spinout/title|General pathology, also called spinout/title|General pathology|investigative pathology, spinout/title|General pathology|experimental pathology or spinout/title|General pathology|theoretical pathology, is a broad and complex scientific field which seeks to understand the mechanisms of injury to cells and tissues, as well as the body's means of responding to and repairing injury. Areas of study include cellular adaptation to injury, necrosis, inflammation, wound healingand neoplasia. It forms the foundation of spinout/link|pathology, the application of this knowledge to diagnose diseases in humans and animals.
The term "general pathology" is also used to describe the practice of both anatomical and
Adaptation to injury
Disease processes may be incited or exacerbated by a variety of external and internal influences, including trauma,
infection, poisoning, loss of blood flow, autoimmunity, inherited or acquired genetic damage, or errors of development. One common theme in pathology is the way in which the body's responses to injury, while evolved to protect health, can also contribute in some ways to disease processes.cite book |author=Ramzi Cotran, Vinay Kumar, Tucker Collins |title=Robbins Pathologic Basis of Disease, Sixth Edition |year=1999 |publisher=W.B. Saunders |isbn=072167335X]
Cells and tissues may respond to injury and stress by specific mechanisms, which may vary according to the cell types and nature of the injury. In the short term, cells may activate specific genetic programs to protect their vital
proteins and organelles from heat shockor hypoxia, and may activate DNA repairpathways to repair damage to chromosomesfrom radiation or chemicals. Hyperplasiais a long-term adaptive response of cell division and multiplication, which can increase the ability of a tissue to compensate for an injury. For example, repeated irritation to the skin can cause a protective thickening due to hyperplasia of the epidermis. Hypertrophyis an increase in the "size" of cells in a tissue in response to stress, an example being hypertrophy of muscle cells in the heartin response to increased resistance to blood flow as a result of narrowing of the heart's outflow valve. Metaplasiaoccurs when repeated damage to the cellular lining of an organ triggers its replacement by a different cell type.
Necrosisis the irreversible destruction of cells as a result of severe injury in a setting where the cell is unable to activate the needed metabolic pathways for survival or orderly degeneration. This is often due to external pathologic factors, such as toxins or loss of oxygen supply. Milder stresses may lead to a process called "reversible cell injury", which mimics the cell swelling and vacuolization seen early in the necrotic process, but in which the cell is able to adapt and survive. In necrosis, the components of degenerating cells leak out, potentially contributing to inflammation and further damage. Apoptosis, in contrast, is a regulated, orderly degeneration of the cell which occurs in the settings of both injury and normal physiological processes.
Inflammationis a particularly important and complex reaction to tissue injury, and is particularly important in fighting infection. Acute inflammation is generally a non-specific response triggered by the injured tissue cells themselves, as well as specialized cells of the innate immune systemand previously developed adaptive immune mechanisms. A localized acute inflammatory response triggers vascular changes in the injured area, recruits pathogen-fighting neutrophils, and begins the process of developing a new adaptive immune response. Chronic inflammationoccurs when the acute response fails to entirely clear the inciting factor. While chronic inflammation can lay a positive role in containing a continuing infectious hazard, it can also lead to progressive tissue damage, as well as predisposing (in some cases) to the development of cancer.
Tissue repair, as seen in
wound healing, is triggered by inflammation. The process may proceed even before the resolution of a precipitating insult, through the formation of granulation tissue. Healing involves the proliferation of connective tissuecells and blood vessel-forming cells as a result of hormonal growth signals. While healing is a critical adaptive response, an aberrant healing response can lead to progressive fibrosis, contractures, or other changes which can compromise function.
Neoplasia, or "new growth," is a proliferation of cells which is independent of any physiological process. The most familiar examples of neoplasia are benign tumorsand cancers. Neoplasia results from genetic changes which cause cells to activate genetic programs inappropriately. Dysplasiais an early sign of a neoplastic process in a tissue, and is marked by persistence of immature, poorly differentiated cell forms. Interestingly, there are many similarities in the gene pathways activated in cancer cells, and those activated in cells involved in wound healing and inflammation.
Choristoma, ectopic tissue, heterotopic tissue, or aberrant tissue, is a mass of histologically normal tissue that is present in an abnormal location.
MeSHclassification [http://www.nlm.nih.gov/cgi/mesh/2007/MB_cgi?mode=&term=Pathological+Conditions,+Signs+and+Symptoms&field=entry#TreeC23 C23.300.250] (pathological conditions, signs and symptoms ]
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